1. Field of the Invention
This invention relates to the field of articles of manufacture suitable for polishing or otherwise improving the uniformity of finish of surfaces of solid objects, particularly those of made of hard materials such as most metals and glass. More particularly, this invention relates to such articles of manufacture comprising size graded abrasive grain fixed to and supported by a resilient backing material, which is itself fixed to and supported by a primary backing material. The primary backing is suitable for joining into belts or cutting into discs, sheets, etc. useful in mechanical or manual operations of the type in which conventional coated abrasives, buffs, or other similar conventional surface finishing tools might also be employed.
2. Technical Background
U.S. Pat. No. 3,607,159 to Haywood describes a resilient, controlled density, porous structure laminated to flexible backing. The structure contains fine abrasive particles adhesively bonded to the surface opposite the backing and distributed within the resilient structure, with the abrasive density varying inversely to the distance from the backing. A protective abrasion-resistant layer is interposed between the abrasive grain and the surfaces of the resilient structure. The resilient, controlled density, porous structure has a resiliency characterized by a 25% compression force in the range from 10-50 pounds per square inch, a density of from 10-30 pounds per cubic foot, and a porosity of from 55-85 percent.
U.S. Pat. No. 3,653,859 to Zimmer et al. describes a high density abrasive-containing foam product which is made by impregnating a low density foam with a slurry of adhesive and abrasive, drying the same below the cure temperature of the adhesive, and then laminating the dried and impregnated foam to a reinforcing backing by heat and pressure, which both densify the foam and effect the lamination, using the abrasive binder adhesive to obtain adhesion between the foam component and the backing component. The initial foam has a 25% compression force value in the range of 10-30 pounds per square inch, and the foam is usually compressed to one quarter or less of its original thickness during the process of making the product.
U.S. Pat. No. 4,038,047 to Haywood describes a complex process of making a suitable resilient backing for an abrasive polishing product. In this process, small particles of resilient foam are packed into a cylinder and densified by an adhesive binder; a thin continuous sheet is peeled from the outer surface of the resulting coherent cylinder of bonded foam; and the resulting sheet is sanded by abrasives to prepare its surface for coating with abrasive grain and binder therefor.
U.S. Pat. No. 4,504,283 to Charvat describes another type of resilient abrasive especially suited to sharpening edged cutting tools. This product utilizes only grit 700 or finer abrasives, and visual discontinuities, such as clusters of cells or voids, on the abrasive surface are stated to be undesirable.